JPS6235555B2 - - Google Patents

Description

Detailed Description of the Invention In a single-acting cylinder in which a loaded object is pushed up by the cylinder extending, and the cylinder is shortened by the weight of the loaded object to lower the object, the inner surface of the cylinder is Conventionally, when the stroke is completed by letting the fluid escape from the unload hole provided in the piston, several piston rings made of alloyed cast iron and having stepped openings have been used.
This is because the cast iron piston ring was needed not only to contain the working internal pressure, but also to prevent the piston ring from being pushed out into the unloading hole by the cylinder working internal pressure when the piston ring passed through the unloading hole. . This piston ring made of cast iron leaks the pressurized hydraulic oil that operates the piston from the sliding part with the inner surface of the cylinder and the stepped opening part, so the pressure inside the cylinder leaks due to the weight of the load object, causing a drop. It is something.

The present invention has been made with the object of minimizing this drop.

The present invention will be explained in detail with reference to FIGS. 1 to 5 showing one embodiment. First, an example of the configuration of a hydraulic circuit is shown. The one shown in FIG. The cylinder C is connected to the tank T by a low-pressure pipe L, and the cylinder C is connected to the pump P by a high-pressure pipe H with a switching valve V provided midway.

The cylinder C is a cylinder body 1 as shown in FIG.
A piston 5 and a piston rod 6 are housed inside, a refueling port 2 is provided at the bottom of the cylinder body 1, an unload hole 3 and a return hole 4 are provided at the top of the cylinder body 1 to complete the cylinder stroke, Two of these holes 3 and 4 are collectively defined as a return port 7. 8
is a piston ring made of alloyed cast iron and has a stepped abutment that is assembled into a piston ring groove provided on the outer diameter of the piston 5.

Reference numeral 9 denotes a synthetic resin piston ring made of a flexible material such as synthetic resin and formed into an annular shape without an abutment, and includes a cylindrical surface portion X that slides in cylindrical contact with the inner diameter surface of the cylinder body 1 and an inner diameter surface of the cylinder body 1. The outer diameter surface is formed by a chamfered tapered guide surface portion Y that does not touch the outer diameter surface.

Examples of synthetic resins with good flexibility in the present invention include synthetic rubber (nitrile rubber), nylon-based synthetic resins, and vinylon-based synthetic resins.

10 is a piston ring groove and a piston ring 8,
9 is the space that is filled with pressurized hydraulic oil. Note that A in FIG. 4 is a piston ring made of a material such as synthetic resin and having a simple rectangular cross section, which is shown for reference purposes.

To explain the operation of the present invention with the above configuration, when the pump P in the hydraulic circuit shown in FIG. 5 is driven to raise the switching valve V, the piston rod 6 of the cylinder C
expands and pushes up the weight W of the loaded object. During the intermediate process of this upward movement, the pressurized hydraulic oil below the piston 5 is moved between the outer diameter of the piston 5 and the cylinder body 1 due to the blocking action of the piston ring 8 and the synthetic resin piston ring 9.
Leakage of pressurized hydraulic oil from the sliding part between the inner surfaces of the cylinder is prevented.

When the cylinder C is further extended and the synthetic resin piston ring 9 passes through the unload hole 3 provided in the cylinder body 1, the flexible synthetic resin piston ring 9 closes the gap 1 in the piston ring groove.
The unload hole 3 is opened by the pressurized hydraulic oil present in the 0 part.
It becomes a state of being pushed inward. However, at this time, since a piston ring 8 made of alloyed cast iron is provided between the piston 5 and the pressurized hydraulic oil located at the lower part of the piston 5, the synthetic resin piston ring 8
Since there is not enough leakage of oil to push the oil into the unload hole 3, the synthetic resin piston ring 9 can pass through the unload hole 3. Next, when the pump P is stopped and the cylinder C continues to be extended through its entire stroke, the sliding part of the piston ring 8 made of alloy cast iron having a stepped opening with respect to the cylinder body 1 and the stepped opening. Since the pressurized hydraulic oil in the lower part of the piston 5 gradually leaks and returns to the tank T through the unloading hole 3, the lower edge of the cylindrical surface of the synthetic resin piston ring 9 eventually coincides with the lower edge of the unloading hole 3.
At this time, a flexible synthetic resin piston ring 9
starts to come into close contact with the inner surface of the cylinder body 1, so leakage of the pressurized hydraulic oil becomes minimal. However, as shown in FIG. 4 for reference purposes, when the lower edge of the outer diameter surface of the synthetic resin piston ring A, which has a simple rectangular cross section, comes to the same position as described above, the piston ring A is moved to the piston ring 8. The pressurized hydraulic oil leaking from the piston groove is pushed outward from the gap 10 side (inside) of the piston groove and is pushed into the unloading hole 3 in the distorted shape shown by the solid line in Figure 4, so the switching valve V is lowered at this time. If the piston ring A is switched to the unload hole 3, defects such as the portion of the piston ring A pushed out into the unload hole 3 may be sheared and cut off.

When the flexible synthetic resin piston ring A is provided on the pressure side of the piston 5 as described above, the synthetic resin piston ring A is pushed out into the unload hole 3. That is, in the process in which the piston 5 moves to the unload hole 3 side and the piston ring A passes through the unload hole 3, a small amount of hydraulic oil leaking from the gap in the piston ring A moves the piston ring A to the unload hole 3 side. Since it has a pushing action, the piston ring A passing through is pushed out into the unloading hole 3 and is damaged.

In order to eliminate the above-mentioned defects, the present invention provides a metal piston ring 8 on the hydraulic side to prevent hydraulic pressure from being applied to the synthetic resin piston ring 9 as much as possible, and allows the piston 5 to pass through the unload hole 3. If you try to hold it in that position,
When there is a force acting on the piston due to the weight of the suspended object, the hydraulic pressure supporting the piston 5 leaks little by little from the metal piston ring 8, and the piston 5 continues to move gradually in the direction of contraction, and the inclined surface of the piston ring 9 eventually Hydraulic pressure acts on the piston ring 9 when it passes the lower edge of the unload hole 3 . At this time, since the boundary section between the inclined surface and the parallel surface (cylindrical surface) of the piston ring 9 is already at the lower edge of the unloading hole 3, the piston ring 9 is not pushed out into the unloading hole 3 and is There is no risk of it getting damaged. This is possible due to the leakage prevention effect of the metal piston ring 8.

However, in the synthetic resin piston ring 9 of the present invention, since the tapered guide surface portion Y provided on the outer diameter portion has already entered the inner diameter surface of the corresponding portion of the cylinder body 1, the synthetic resin piston ring 9 is It is almost possible to prevent the ring 9 from being pushed out into the unloading hole 3. Therefore, at this time, even if the switching valve V is switched to the downward direction, the synthetic resin piston ring 9 will not be defective due to shearing or the like.

As described above, the present invention aims to improve the conventional cast iron material by meaningfully combining the shape of the synthetic resin piston ring and the positional relationship with the conventionally used piston ring having a stepped opening made of alloyed cast iron material. Compared to a method using several piston rings made of aluminum, this method has the effect of minimizing the drop of the cylinder due to leakage of cylinder internal pressure caused by the weight of the load object.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the cylinder, Fig. 2 is a partial cross-sectional view of the cylinder during unloading according to the present invention, Fig. 3 is a cross-sectional view of the piston ring according to the present invention, and Fig. 4 is a rectangular piston ring for explanation reference. FIG. 5 is a sectional view of a portion showing a state of being pushed out into an unloading hole, and FIG. 5 is a hydraulic circuit diagram. 1 is a cylinder body, 2 is an oil supply port, 3 is an unloading hole, 4 is a return hole, 5 is a piston, 6 is a piston rod, 7 is a return port, 8 is a piston ring made of alloyed cast iron material, 9 is a synthetic resin piston 10 is a gap, A is a rectangular piston ring for reference, X is a cylindrical surface portion of the piston ring, and Y is a tapered guide surface portion of the piston ring.

Claims (1)

[Claims] 1. A piston with a piston rod is installed in a cylinder body that has a refueling port at one end and an unloading hole and a return hole at the other end so as to be extendable and retractable, and a metal An annular piston ring made of synthetic resin with no abutment, which is loosely fitted into the piston ring groove of the piston with a space between the metal piston ring and the pressurized side, has good flexibility. Made of synthetic resin, the upper outer diameter surface touches the inner surface of the cylinder body, and the lower outer diameter surface is an inclined surface with the lower end facing the center of the piston, and this inclined surface slides without touching the inner surface of the cylinder body. It is characterized by that it is made to
Hydraulic cylinder with synthetic resin piston ring.